Oh yes!!! Night riding is so much fun!!! Just make sure you have ample light and are familiar with the trails. Night riding when you don't know where you are going is no fun and an easy way to get hurt.
Ride with a buddy if you can. That being said, i have ridden alone numerous times at night and it is a freakin blast!

I just let them take their time. No use rushing the slower riders as it does not inspire confidence. I'll lead or I will let them lead. The most important thing is to just be supportive and patient. Just remember we have all been there at one point.
My friends do ride quicker than I do. They do wait but I also do let them know that if they feel like going on, keep pinning it.

Same with me. I'll always move out of the way for the downhillers as I would want the same when I point downwards. For climbers...well if do generally slow down and move over, particularly on sections where I know it is a bit of work to get moving again.
Either way, depends on the situation. At the end of the day, we all just want a great ride so no use gettin worked up about trivial things.

Got that book! Great book and has helped me out quite a bit when I first started out. Best thing to do is a read a couple of the topics and then go out and ride. With videos like this, it helped me develop some of the required skills. Sure there are few faults here and there but what instructional video doesn't? I'll keep this one on my list. I usually direct people to some of the videos as it shows it better than I can explaining it.